(a) Field of the Invention
The present invention relates to a CMOS image sensor and a manufacturing method thereof.
(b) Description of the Related Art
An image sensor is a semiconductor device converting optical images into electrical signals and, typically manufactured in a type of a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor.
The charge coupled device is an integrated circuit containing an array coupled capacitors. Each capacitor stores and transfers electric charge to on or other of its neighbors. In the meantime, the CMOS image sensor is a device adopted a switching mechanism sequentially detecting output using MOS transistors as many as the number of pixels with the CMOS technology which uses the control circuit and signal processing circuit as peripheral devices.
The CMOS image sensor is comprised of a photo-sensing region for detecting the light, a logic circuit area for processing to convert the light into electric signals, and color filters arranged over the photo-sensing region. The photo-sensing region generates photoelectric charges using the light from outside and accumulates the charges. The color filter array (CFA) includes the three filter elements of red, green, and blue colors or yellow, magenta, and cyan colors.
In this case, the red, green, and blue colors filters are formed by exposing and developing the red, green, and blue photo resists formed on the photosensing region. Unlike other processes, however, the photo resist pattern becomes the color filter by itself through the process for forming the color filters, such that when the three photo resist patterns should be formed it is required to rework for forming any of three colors filters, the previously formed photo resist pattern(s) as well as the current photo resist must be removed.
Also, since the color filter-forming processes should be carried out three times or more while the metal on the pad part is exposed such that the metal is likely to be eroded by the developer solution. The damage of the metal pad causes various problems in wire bonding and probe test processes.
The U.S. Pat. Nos. 5,719,074 and 4,600,833 have disclosed typical image sensors and methods for manufacturing the image sensors.